Dark Green Leafy Vegetables for Calcium: Many of us are avoiding dairy these days due to lactose intolerance, dairy allergies, choosing to live a vegan life style or a combination of these factors. Dark green leafy vegetables can be a great source of calcium along with beans. Some dark greens like kale, mustard greens and turnip greens have an absorption rate of calcium of over 50%. Many dairy sources (cow’s milk for instance) has an absorption rate of about 32%.